CSN11101Network Systems and ServicesWeek 2: Introduction/Linux Basics

Module Leader: Dr Gordon Russell

Networked Services

• Main focus is Linux system administration.• Uses “linuxzoo.net” for practical exercises.• Pre-requisites for this module are:

– Basic OS concepts (partitions, virtual memory, processes, etc).

– Networking basics (IP, Ethernet)

Recommended Text• Variety of good books on system administration.

• Recommended book for general admin:

UNIX SYSTEM ADMINISTRATION HANDBOOK:Third Edition – EVI NEMETH et allPrentice Hall, ISBN 0-13-020601-6

• Nemeth also wrote “Linux System Administration Handbook”. Its just as good, cheaper, and lighter.

• Apache and DNS is best read online.

Elements Covered

• The module covers some important aspects of system administration for Linux machines:– Basic Unix / command prompt– Linux user and network administration.– Network Security– Linux-based DNS– Apache Web Server administration.– Hacking Techniques– Email

Timetable

• You should attend 2 hours of lectures + 2 hours of tutorials per week.

• Lectures will be mostly “lecturing”, but will also include group tutorial sessions.

• Attendance will be taken.

Tutorials

• These run using any networked PCs.• Tutorials involve you being the administrator on your

own Linux machine.• This is available online from http://linuxzoo.net

This is an in-house system, and in some ways an experimental system, and this is also a new module. I expect that there may be initial technical problems to be fixed. I would appreciate your patience and constructive feedback.

Assessment

• The assessments involve both coursework and an exam. The weighting is 50:50.

• The coursework involves an on-line supervised exercise where you need to make specified changes to a Linux installation.

• The exam is a short-answer exam using 20 questions.

• Both pieces of work are OPEN BOOK.

Lectures

• The lectures are 1-2 hours long. • Lectures are not the source of all knowledge.• You need to do some reading on your own, and

to practice with the Linux machines.• If you don’t attend the tutorials and lectures, and

practice what you have learned right from week 1, you will struggle with this module.

Weeks 2 - 7

Week Lecture Class Tutorials

2 Intro / Linux basics Use of Linux intro1 intro2

3 Users, Permissions, Processes, Pipes

wildcard permission

4 Basic Administration Concepts

pipe vi

5 Networking essential admin

6 Firewalls + Security net fwall

7 DNS dns

Weeks 8 - 15Week Lecture Class Tutorials

8 Essential Apache diag

9 **Reading Week** Support Lecture

Apache1

10 Using Apache ** PRACTICAL EXAM **

11 Hacking Apache2

12 Email Revision

13 Revision** PRACTICAL RESIT DEADLINE **

Revision

14-15 Exam Period

Practical Assessment

• Practical Assessment for Linux:– In-Class OPEN BOOK timed assessment.– This will happen in week 11.– 1-2 hour Linux network and Linux configuration and

troubleshooting.– This is worth 50% overall

• A capped resit attempt is offered if you fail the practical– Submission is in week 13. Max score is half marks.– It is an essay based coursework.

Running the Virtual Machines

• Visit http://linuxzoo.net/• Change the drop-down in the control box to “Register for an

account”• Read the instructions and click the link at the bottom.• You must provide your email address, name, matriculation

number, and correctly select your programme.• Get the AUTH CODE from the lab tutor.

User Registration

Red means it went wrong. If you are still on this page when you click “Register” then it went wrong.

Check Your Account

(FULL) means your auth code worked. (GUEST) means you need “Your Profile” then re-enter the auth code. Without the code you may get less system time and a poor queue position.

Queue for a machine

Boot the machine

Booting takes time

Connect to your machine

Minimise the box

Why A Command Prompt?

• Linux does have a graphical interface.• However it is faster, easier, and more powerful

to use commands at a prompt to configure a server.

• Commands do mean a steep learning curve.• Editing is tough!

X Windows

Unix Flavours

• There are many flavours of unix and Linux.• Linux “distributions” include:

– Fedora– Redhat– Novell SUSE– Gentoo

• Different distributions have things in common but some differences. The distributions selection is often down to personal choice and “what my friend uses”.

Telnet in the virtual machines

• Telnet is quite clever and usually no matter what OS and keyboard you have things just seem to “work”.

• Sometimes however telnet gets confused.• If you ever have a problem where cursor keys

stop working, or your editor corrupts the screen try these magic commands (you don’t type the “>”):

> export TERM=vt100> tset

The Tutorials.

Tutorials Username

• The advanced tutorials use the root user (password secure).

• The basic tutorials create a user called “demo”, password “demo”.

• If you are not logged in you can just log in as demo.• If you are logged in as root:

> su - demo

Demo> …..

Demo> <CTRL><D>

>

Useful commands:

• ls• cat• cal• date• pwd• more• cd

• mkdir• cp• mv• rm• rmdir• man

Running a tutorial Machine

• Your machine is a VIRTUAL machine.• Your VM uses a shared computer resource.• The resource is limited!• Do not go crazy (do not recompile the world).• Priority goes to those in B56 during a tutorial.• Your virtual disk is not reliably preserved

between sessions. Do not save your life work on it.

The Basics

• Before your machine operates it must BOOT.• As it boots things are started up.• Only when the boot process completes will the

system be fully operational.• When you are finished, a machine can be

shutdown or halted.– Shutdown – does it nicely and cleanly– HALT – pulls the power out the back.

The PROMPT

• Once you log into your machine, you are at the prompt. Here you can perform your commands.

• Everything on linux is either a file or a directory.• A file which is executed becomes a process.• Processes can be seen as files too.• Devices, such as scanners and hard drives are

also files.

> ls /

bin dev home lost+found mnt root selinuxtmp var boot etc lib misc proc sbinsys usr

• Directories use / in linux (like Windows uses \).• No volumes in linux (like C: or A: )• / is called the root directory.• ls splits the files either by line or in this case by

tabs.

Directories• /bin : This contains commands a user can run, like ‘ls’, but which

might be needed during boot.• /dev : This contains devices, like the mouse.• /home : This is where users store their files.• /tmp : Temporary storage for users and the system• /var : System files which can change.• /etc : System config files which don’t change• /lib : Where all the system libraries live• /proc : Files which represent the running system (like processes).• /sbin : Commands which only an administrator would want.• /usr : Commands which are never needed during bootup.

> cal

August 2008Su Mo Tu We Th Fr Sa 1 2 3 4 5 6 7 8 910 11 12 13 14 15 1617 18 19 20 21 22 2324 25 26 27 28 29 3031

Redirection• If you end a command with “>”, its output goes to a file.• If you end a command with “<“, its input comes from a file.

$ lsa$ cal > b$ lsa b$ cat b August 2008Su Mo Tu We Th Fr Sa 1 2 3 4 5 6 7 8 910 11 12 13 14 15 1617 18 19 20 21 22 2324 25 26 27 28 29 3031

Prompts

• When explaining commands, we usually put a prompt character before it to make it clear that the command has to be typed.

• You can set the prompt to anything, but in examples prompts like $ or > are common.

• Don’t type the first > or $ you see:

$ ls

$ cal

> ls

> cal

Parameters

• Some commands change behaviours with different parameters.

• If a parameter relates to a file, then it is called a “parameter”.

• However, if the parameter changes the behavour of the program, it is instead called an “option” or “flag”.

Flags$ cal August 2008Su Mo Tu We Th Fr Sa 1 2 3 4 5 6 7 8 9...

$ cal -m August 2008Mo Tu We Th Fr Sa Su 1 2 3 4 5 6 7 8 9 10...

Man pages

• If you don’t know what options or flags are possible for a command, use “man”

• For instance, to find out what flags cal uses, do:

$ man cal• To get out of man, press “q”. Space shows you

more of the information.

Man -k

• You can keyword search for commands• For instance, what commands show a calendar?

$ man -k calendarcal (1) - displays a calendarcal (1p) - print a calendardifftime (3p) - compute the difference…

Directories

$ lsa b$ mkdir d1$ lsa b d1$ cd d1$ pwd/home/demo/d1

$ pwd/home/demo/d1$ cd ..$ pwd/home/demo/t$ lsa b d1$ rmdir d1$ lsa b

Directory characters• Absolute location (Starts with “/”)cat /home/demo/z1cat ~demo/z1

• Relative location (where z2 is a directory)cd /homecat demo/z1

cd /home/demo/z2cat ../z1

Wildcards

• Parameters which match filenames don’t have to be complete. You can pattern match with the characters “?” for a single character and “*” for a number of characters.

$ lsaaa aab abb$ ls aa?aaa aab$ ls a*aaa aab abb

Wildcard [set]

• You can pattern match with a set of characters. For instance, you want files which end with a or b.

$ lsaaa aab aac zzb zzc$ ls aa[ab]aaa aab$ ls *[ab]aaa aab zzb

Tutorials Week 2

• You should now be able to complete– Intro1– Intro2– Wildcard (not links)

Discussions

• Who is using linux?

Discussions

• What is Linux for?–Desktop

–Software Developers

–Servers